Currently CONCATENATE.RANGE seems the only (native) way of concatenating a (more or less dynamic) number of values with a delimiter. Unfortunately it only works with a cell / cell range. If a list form element uses a variable as target and the selected values should be concatenated, the variable has to be put into a cell first ("=@varListSelection") so that this cell then can be referenced in CONCATENATE.RANGE. It would be much easier, if the variable could be used directly in this function. Not only variables, it should have no restrictions, meaning, it should also resolve named ranges and functions (e.g. concatenate all elements that are returned by PALO.SUBSET(...) function).
Instead of enhancing CONCATENATE.RANGE It would be also suitable to create a new function, that maybe then has some further functionality, including:
allow more than single character as delimiter, e.g. comma + space (", ")
ignore empty
simply return value without concatenating, if value is no array (so that no IF() has to be built, when the variable could be an array or single value, like in a list form element)
